Rubber composition containing 2, 6-bis (2&#39;-hydroxy-3&#39;-tert butyl-5&#39;-lower alkylbenzyl)-4-methyl phenols as stabilizers



RUBBER COMPOSITION CONTAINING 2,6-BIS(2'- HYDROXY-3-TERT BUTYL--LOWER ALKYL- BENZYL)-4-METHYL PHENOLS AS STABILIZERS Frank A. v. Sullivan, Darien, and Arnold R. Davis, Riverside, Conn., assignors to American Cyanamid Company, New York, N. Y., a corporation of Maine Application February 5, 1954 Serial No. 408,580

12 Claims. (Cl. 260-810) No Drawing.

OH OH wherein R is methyl, ethyl or n-propyl.

These compounds are useful as antioxidants and particularly as antioxidants for rubber, resins, waxes, lubrication oil, etc.

According to the invention, the compounds may be prepared by reacting at substantially room temperature two moles of a Z-tertiary butyl-4-lower alkyl-phenol with one mole of 2,6-di-(hydroxy-methyl) para cresol. The 2-tertiary butyl-4-lower alkyl phenols which may be employed are 2-tertiary butyl-4-methyl phenol, Z-tertiary butyl-4-ethyl phenol and 2-tertiary butyl 4 n propyl phenol. The reactants are all well known and are commercially available.

The invention is further illustrated by the following specific examples to which it, however, it not to be limited.

EXAMPLE 1 Preparation of 2,5-bis-(Z'Jzydroxy-BGtertiary butyl-5'- methyl-benzyl)-4-methyl phenol 73 grams (0.448 mole) of 2-tertiary'butyl-4-methyl phenol paracresol are suspended in 150 ml. of heptane,

Preparation of 2,6-bis(2-hydroxy -3 tertiary butyl-5- ethyl-benzyl)-4-methyl phenol 80 grams (0.448 mole) of Z-tertiary butyl-4-ethylphenol are suspended in 175 ml. of heptane and to this suspension is added 37.5 grams (0.224 mole) of 2,6-di- (hydroxy methyl) para-cresol with 11.5 ml. of concentrated hydrochloric acid and 1 gm. of sodium lauryl sulfate (Dupanol C) as a dispersing agent. The reaction mixture is digested at 25 C.30 C. for 16 hours. At the end of this time, the crude product was filtered, washed and dried. The yield obtained is 70%, the M. P. 130l35 C. On recrystallization from fresh heptane, 2,6-bis(2-hydroxy 3' tertiary butyl-5'-ethyl-benzyl) -4- methyl phenol melted at l40141 C.

EXAMPLE 3 Preparation of 2,6-bis(2'-hydroxy-3'tertiary butyl-5'-npropyl-benzyl) -4-methyl phenol 86 grams (0.448 mole) of 2 -tertiary-butyl-4-n-propyl phenol are suspended in 200 ml. of heptane and to this suspension is added 37.5 grams (0.224 mole) of 2,6-di- (hydroxymethyl) paracresol with 11.5 ml. of concentrated hydrochloric acid and 1 gram of Dupanol C. The reaction mixture is digested at 25-30 C. for 18 hours. At the end of this time, the crude product is filtered, washed and dried. The yield is 72%, the M. P. 120123 C. On recrystallization from fresh heptane, the product melted at 132 C.

The 2,6-bis (2'-hydroxy-3'-tertiary butyl -5'-lower alkylbenzyl)-4-methyl phenols of the present invention may be utilized in a number of difierent ways to retard the normal rate of oxidation in rubber. The term rubber as used in this description refers to vulcanizable natural and synthetic rubber. During the compounding of vulcanizable rubber, the antioxidant may be added at any stage, although for all practical purposes it is added fairly early. It has been found that the antioxidant is advantageously added to the vulcanizable rubber along with sulfur and an acceleration assistant. Further, it may be dissolved in a suitable solvent and sprayed or painted onto a vulcanized rubber article. This article may also be preserved against normal oxidation by dipping it in a suitable solution of antioxidant.

To further illustrate the applicability of the antioxidants to vulcanizable rubber, 2,6 bis(2 hydroxy 3- tertiary-butyl-S'-methyl-benzyl)-4-methyl phenol, which is henceforth designated as antioxidant A, was incorporated into a typical rubber batch having the following formulation:

Pale crepe 100 Fine precipitated calcium carbonate 60 Titanium dioxide 20 Zinc oxide 5 Sulfur 3 Stearic acid 1 Benzothiazyl disulfide 1 However, the examples are presented by way of illustration and not of limitation.

EXAMPLE 4 EXAMPLE 5 In this example, the batch of rubber formulated as in Patented Jan. 7, 1958 3 Example 4 is vulcanized by curing for thirty minutes at 141 C. except the antioxidant is omitted. The sample was tested for tensile strength and creep. These results similarly appear in the tables below.

Antioxidant. A

In Tables 1 and 2 above, it becomes readily apparent that the vulcanizable rubber composition which has been cured, shows a marked lowering of the rate of oxidation when an antioxidant of this invention is incorporated into a vulcanizsble rubber composition. The higher percentage of tensile strength retained indicates the better ageing quality of a rubber. Similarly, the lower creep value percentage indicates better ageing qualities due to the antioxidant additive.

While in the example above, 1.5 parts of antioxidant per l parts of rubber were incorporated, it has been found that a range of from about 0.2 to 3.0 parts of antioxidant per parts of rubber may be advantageously added, depending upon the type of vulcanizable rubber type. For all practical purposes, a range of from 1.0 to 1.5 parts of antioxidant is quite suitable.

The temperature of vulcanization or curing may be permitted to vary in a range of from about C. to 200 C. However, it is preferred that a range of from about C. to C. be employed to prevent undue scorching of the rubber composition within the desirable time to effect the curing operation.

We claim:

1. In a process for retarding the normal oxidation of a vulcanized natural rubber, the steps which comprise adding to a vulcanizable natural rubber composition a compound represented by the formula:

(OHa)s-C- CHr- C-(CH3):

l l I n OH: R

said vulcanized rubber, said antioxidant being present in amounts of from about 0.2 to 3.0 parts per 100 parts of rubber.

2. A process according to claim 1 wherein the antioxidant is 2,6-bis(2-hydroxy-3'-tertiary-butyl-5'-methylbenzyl) -4-methyl phenol.

3. A process according to claim 1 wherein the antioxidant is 2,-6-bis(2'-hydroxy-3-tertiary-butyl-5'-ethylbenzyl) -4-methyl phenol.

4. A process according to claim 1 wherein the antioxidant is 2,6-bis(2'hydroxy-3'-tertiary-butyl-S-n-propyl)-4-methyl phenol.

5. An unvulcanized vulcanizable natural rubber composition characterized by the retardation of the normal rate of oxidation comprising vulcanizable natural rubber, sulfur and an antioxidant represented by the formula of claim 1, said antioxidant being present in amounts of from about 0.2 to 3 parts per 100 parts of said rubber.

6. The unvulcanized vulcanizable natural rubber composition of claim 5 wherein the antioxidant is 2,6-bis(2'- hydroxy-S'-tertiary-butyl-5 '-methyl-benzy1) -4-methyl phcnol.

7. The unvulcanized vulcanizable natural rubber composition of claim 5 wherein the antioxidant is 2,6-bis(2- hydroxy-3 '-tertiary-butyl-5 -ethy1-benzyl '4-methyl phe- 1101.

8. A vulcanized natural rubber composition containing in said rubber composition of from about 0.2 to 3.0 parts of antioxidant per 100 parts of rubber, said antioxidant being represented by the formula of claim 1, and characterized by a marked lowering of the rate of oxidation for a similar composition from which the compound is omitted.

9. According to claim 8, a vulcanized natural rubber composition containing in the rubber composition of from about 0.2 to 3.0 parts of 2,6-bis(2'-hydroxy-3'- tertiary-butyl-S'-methyl-benzyl)-4-methyl phenol per 100 parts of rubber.

10. According to claim 8, a vulcanized natural rubber composition containing in the rubber composition of from about 0.2 to 3.0 parts of antioxidant per 100 parts of rub her, said antioxidant being 2,6-bis(2'-hydroxy-3-tertiarybutyl-5'-ethyl-benzyl)-4-methyl phenol.

11. According to claim 8, a vulcanized natural rubber composition containing in the rubber of from about 0.2 to 3.0 parts of antioxidant per 100 parts of rubber, said antioxidant being 2,6-bis(2-hydroxy-3-tertiary-butyl-5-n-propyl-benzyl)-4-methyl phenol.

12. A composition containing natural rubber and as an antioxidant, a compound of the formula:

| CHa CH:

where R is tertiary butyl.

References Cited in the file of this patent UNITED STATES PATENTS 2.538.355 Davis et al. Jan. 16 1951 

1. IN A PROCESS FOR RETARDING THE NORMAL OXIDATION OF A VULCANIZED NATURAL RUBBER, THE STEPS WHICH COMPRISE ADDING TO A VULCANIZABLE NATURAL RUBBER COMPOSITION A COMPOUND REPRESENTED BY THE FORMULA: 